Ripping earth using large tracktype tractors has traditionally been a difficult and time consuming job, even for very skilled operators. Because the process necessarily involves unseen underground components, the ripper can encounter a very loose area of earth in which it could be moved relatively easily. Alternatively, the ripper could get caught up on underground obstacles, such as large boulders or bedrock, which pose the likelihood of increasing the drag on the machine, sometimes to the extent that the engine stalls and the tractor stops. When the engine stalls, the ripper generally has to be lifted from the earth and reset at a different point after reinitiating movement of the tractor, which can lead to costly losses of both time and fuel. A skilled operator can only prevent these inefficiencies to the degree that they become aware of a deceleration of the tractor prior to the engine stalling. This awareness usually requires a high degree of experience and familiarity with the machine and also a high degree of force on the machine before any outward signs are evidenced to the operator. However, in many instances, the operator has insufficient time to react by changing the ripper configuration to prevent a stall.
Work machine control strategies to increase efficiency are well known in the art. For instance, co-owned U.S. Pat. No. 5,974,352 is aimed at controlling operation of a bucket on a work machine to increase efficiency through the use of sensed force angles and magnitudes and altering the bucket position in response to the net force vector on the bucket. A net force vector on a loader bucket is determined based upon sensor inputs to an electronic controller. Bucket tilt and lift commands during contact with a pile of material are modified responsive to differences between the force vector and a target angle. However, this control strategy described generally for wheel loaders is not directly transferable to ripping operations that are based on much different considerations.
In another control example U.S. Pat. No. 4,062,539 teaches a method of automating control of a ripper in piercing and digging modes, respectively. This reference teaches movement of the ripper to a preset angle to initiate either a piercing or digging operation. This reference also teaches the concept of raising the ripper to avoid an overload condition, and re-lowering the ripper when the drag load decreases below some predetermined threshold. But this reference fails to recognize that vertical forces on the ripper and tilt control of the ripper might be exploited to achieve improved efficiencies.
The present disclosure is directed to one or more of the problems or shortcomings described above.